Question

It is required to hold four point charges +q , in equilibrium at the corners of a square.Find the point charge that will do this if placed at the centre of the square?

Answer 1

$\frac{2kqx}{ {a}^{2} } = \frac{k {q}^{2} }{ {a}^{2} } + \frac{k {q}^{2} }{ {a}^{2} } + \frac{k {q}^{2} }{ {2a}^{2} } \\ x = \frac{5q}{4}$